Carbon dioxide gas has been injected into liquids, particularly water, for many purposes. For example, carbonated beverages, including water, beer and the like, have been made by injection of CO.sub.2. See for example, U.S. Pat. Nos. 889,516, 2,226,958 and 2,252,313. Lime tainted water has been treated to reduce deposits and contamination of vessels and tubes. This was often done by using the by-products of combustion. See for example, U.S. Pat. Nos. 3,208,935 and 3,976,445. None of the prior methods provide proper control of the carbonization process. Processes using the by-products of combustion are particularly cumbersome. A water stream has also been sparged with CO.sub.2 in an unpressurized sump or low pressure pipe. Sparging efficiency in such an operation has been low.